1.Q. Why carbon form covalent bond by sharing electron?
Ans: Carbon has four electrons in its outermost shell and needs to gain or lose four
electrons to attain noble gas configuration.
(i) it could gain four electrons forming C4-
anion. But it would be difficult for the nucleus with six protons to hold on to ten
electrons, that is, four extra electrons.
(ii) It could lose four electrons forming C4+ cation.
But it would require a large amount of energy to remove four electrons leaving behind a
carbon cation with six protons in its nucleus holding on to just two electrons.
Hence, it is difficult for the carbon to lose or gain four electrons therefore carbon form
covalent bond by sharing electron.
2.Q. Why do covalent compounds are in gaseous or liquid state at normal temperature
and pressure.
Ans: due to Weak Vanderwaal’s forces present between the molecules of covalent
compounds.
3.Q. Why do covalent compounds have less melting and boiling points?
Ans: As energy required breaking the crystal is less due to the presence of weak
Vanderwaal’s force.
4.Q. Why do covalent compounds are bad conductors of electricity?
Ans: Due to the absence of free electrons or free ions.
5.Q. Why graphite has high melting point?
Ans: Within each layer of graphite, every carbon atom is joined to three others by strong
covalent bonds. This forms a pattern of interlocking hexagonal rings. The carbon atoms
are difficult to separate from one another. So graphite also has high melting point.
6.Q.Why is diamond known as the hardest metal?
Ans: Each carbon is linked to four other carbon atoms forming regular and tetrahedral
arrangement and this network of carbon atoms extends in three dimensions and is very
rigid. This strong bonding is the cause of its hardness and its high density.
7.Q.Define term allotropy?
Ans: Allotropy is the property by virtue of which an element exist in more than one form
and each form has different physical properties but identical chemical properties. These
different forms are called allotropes. The two common allotropic forms of carbon are
diamond and graphite.
src-mountabupublicschool.net
Ans: Carbon has four electrons in its outermost shell and needs to gain or lose four
electrons to attain noble gas configuration.
(i) it could gain four electrons forming C4-
anion. But it would be difficult for the nucleus with six protons to hold on to ten
electrons, that is, four extra electrons.
(ii) It could lose four electrons forming C4+ cation.
But it would require a large amount of energy to remove four electrons leaving behind a
carbon cation with six protons in its nucleus holding on to just two electrons.
Hence, it is difficult for the carbon to lose or gain four electrons therefore carbon form
covalent bond by sharing electron.
2.Q. Why do covalent compounds are in gaseous or liquid state at normal temperature
and pressure.
Ans: due to Weak Vanderwaal’s forces present between the molecules of covalent
compounds.
3.Q. Why do covalent compounds have less melting and boiling points?
Ans: As energy required breaking the crystal is less due to the presence of weak
Vanderwaal’s force.
4.Q. Why do covalent compounds are bad conductors of electricity?
Ans: Due to the absence of free electrons or free ions.
5.Q. Why graphite has high melting point?
Ans: Within each layer of graphite, every carbon atom is joined to three others by strong
covalent bonds. This forms a pattern of interlocking hexagonal rings. The carbon atoms
are difficult to separate from one another. So graphite also has high melting point.
6.Q.Why is diamond known as the hardest metal?
Ans: Each carbon is linked to four other carbon atoms forming regular and tetrahedral
arrangement and this network of carbon atoms extends in three dimensions and is very
rigid. This strong bonding is the cause of its hardness and its high density.
7.Q.Define term allotropy?
Ans: Allotropy is the property by virtue of which an element exist in more than one form
and each form has different physical properties but identical chemical properties. These
different forms are called allotropes. The two common allotropic forms of carbon are
diamond and graphite.
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